Stop using v8 APIs deprecated around engine version 4.3 and switch to modern equivalents.

node-compress-buffer-test
✔ basic compress
✔ basic uncompress
✔ compress with compression levels
✔ string exceptions
✔ compress short
✔ errors

OK: 11 assertions (11ms)

Tested on node v6.9, v8, v10, v12, but even earlier node version compatibility might be broken, hence new major version.